You have such an interesting topic, I wanted to comment. In some ways, it surprising that this topic has not arisen in say, military circles. The flow physics encompasses many interesting effects such as turbulence at the small scales (turbulent eddys can bind up tiny virus particles). Also, this is a Mach zero flow field, so the boundary conditions (forward and reverse acoustic wave travel have a strong effects on the flow) become important. The speech or breathing driven flow implied time-dependent forcing of the flow field. Also, humidity and droplet dynamics must be included. Of course, viscosity and "stick-tion" are important near the PPE surfaces. Of course, an inclusion or virus survivability based on changing environmental conditions is also very, very interesting. I am pleased to learn that someone is pursuing this avenue of research, I am also curious as to whether or not you are mounting an experimental effort.

Thanks Douglas! Currently only numerical effort, as looking to run extensive parameter optimisations of the geometry (shield). We're following a 'minimal viable product' approach (blended with scientific validation). We're looking for sufficiency, not cutting-edge (in other words).

I've tried in an amateur fashion to visualise 'theatre smoke' while talking but I don't think I can capture the dominant motion, but as I haven't done experiment methods before I'm guessing I'm missing something.

Depending on whether I can get collaborators will dictate the the strategy. We're very underfunded and could probably spend that money in more effective ways than proving the science (unfortunately).